Compliant electrostatic transfer head with defined cavity

Background

Field

Embodiment described herein relate to micro devices. More particularly embodiments relate to a compliant electrostatic transfer head array and a method of transferring micro devices to a receiving substrate.

Background Information

Integration and packaging issues are one of the main obstacles for the commercialization of micro devices such as radio frequency (RF) microelectromechanical systems (MEMS) microswitches, light-emitting diode (LED) display systems, and MEMS or quartz-based oscillators. Traditional technologies for transferring of devices include transfer by wafer bonding from a transfer wafer to a receiving wafer. Such implementations include “direct printing” and “transfer printing” involving wafer bonding/de-bonding steps in which a transfer wafer is de-bonded from a device after bonding the device to the receiving wafer. In addition, the entire transfer wafer with the array of devices is involved in the transfer process.

Other technologies for transferring of devices include transfer printing with elastomeric stamps. In one such implementation an array of elastomeric stamps matching the pitch of devices on a source wafer are brought into intimate contact with the surface of the devices on the source wafer and bonded with van der Walls interaction. The array of devices can then be picked up from the source wafer, transferred to a receiving substrate, and released onto the receiving substrate.

In another implementation, the technology for transferring of devices is enabled by an array of electrostatic transfer heads as described in U.S. Pat. No. 8,415,767. As described, an array of electrostatic transfer heads may be formed from a silicon-on-insulator (SOI) substrate. Furthermore, the array of electrostatic transfer heads may be made compliant such that each silicon electrode is deflectable into a cavity between a base silicon substrate and the silicon electrode. In this manner, each compliant electrostatic transfer head can compensate for variations in height of the devices during the transfer process.

Summary

A compliant electrostatic transfer head, method of forming a compliant electrostatic transfer head, and a method of transferring one or more micro devices to a receiving substrate are described. For example, the receiving substrate may be, but is not limited to, a display substrate, a lighting substrate, a substrate with functional devices such as transistors or integrated circuits (ICs), or a substrate with metal redistribution lines. In an embodiment, a compliant electrostatic transfer head includes a base substrate, a cavity template layer on the base substrate, a first confinement layer between the base substrate and the cavity template layer, and a patterned device layer on the cavity template layer. The patterned device layer includes an electrode that is deflectable toward a cavity in the cavity template layer. In an embodiment, a second confinement layer is between the cavity template layer and the patterned device layer. The second confinement layer may span along a top surface of the cavity template layer and directly above the cavity. The second confinement layer may additionally span along sidewalls of the patterned device layer. In an embodiment, the cavity includes substantially vertical sidewalls.

The second confinement layer may be formed directly on the cavity template layer. A spring support layer may optionally be located between the cavity template layer and the patterned device layer for structural support. In such a configuration, an insulating layer may be provided between the spring support layer and the patterned device layer to electrically insulate the patterned device layer from the spring support layer.

In some embodiments the compliant electrostatic transfer head includes a bipolar electrode configuration. For example, the patterned device layer may include a pair of electrodes that is deflectable toward the cavity in the cavity template layer. The pair of electrodes may include a first electrode lead integrally formed with a first mesa structure protruding above the first electrode lead, and a second electrode lead integrally formed with a second mesa structure protruding above the second electrode lead. The patterned device layer may additionally include a first trace interconnect integrally formed with the first electrode and a second trace interconnect integrally formed with the second electrode.

The compliant electrostatic transfer head may have a variety of electrode beam profiles. For example, the first and second electrodes may form an electrode beam profile extending between the first and second trance interconnects. In an embodiment, each of the first and second electrodes includes a double bend, which may be in an S-shape configuration. In an embodiment, the first and second mesa structures are separated by a trench characterized by a width of 1.0 μm or less, and the trench is filled with a dielectric material.

In an embodiment, a method of forming a compliant electrostatic transfer head includes patterning a device layer to include an electrode beam provide above a patterned cavity template layer, and etching a cavity in the patterned cavity template layer beneath the electrode beam profile to expose a first confinement layer beneath the patterned cavity template layer, with the first confinement layer functioning as an etch stop layer during etching the cavity. Patterning the device layer may include forming a pair of electrodes, each including an electrode lead and a mesa structure. A second confinement layer may additionally span along a top surface and sidewalls of the cavity template layer between the patterned device layer and the patterned cavity template layer. In an embodiment, the second confinement layer is etched to expose the patterned cavity template layer prior to etching the cavity, and the second confinement layer also functions as an etch stop layer during etching the cavity.

In an embodiment, prior to patterning the device layer to include the electrode beam profile, a first wafer stack including the device layer is bonded to a second wafer stack including the patterned cavity template layer, the first confinement layer, and the second confinement layer. For example, bonding may be accomplished by fusion bonding.

Brief description of the drawings

FIG. 1A is a plan view illustration of a micro pick up array including an array of bipolar compliant electrostatic transfer heads in accordance with an embodiment.

FIG. 1B is a plan view illustration of a bipolar compliant electrostatic transfer head with a double sided clamped beam including a pair of silicon electrodes with double bends and a mesa joint supported by a spring support layer in accordance with an embodiment.

FIG. 1C is a cross-sectional side view illustration taken along transverse line C-C of the bipolar compliant electrostatic transfer head illustrated in FIG. 1B in accordance with an embodiment.

FIG. 1D is a cross-sectional side view illustration taken along longitudinal line D-D of the bipolar compliant electrostatic transfer head illustrated in FIG. 1B in accordance with an embodiment.

FIG. 2 is a plan view illustration and cross-sectional side view illustration taken along line A-A of a bipolar compliant electrostatic transfer head with cantilever beam and continuous joint supported by a spring support layer in accordance with an embodiment.

FIG. 3 is a plan view illustration and cross-sectional side view illustration taken along line A-A of a bipolar compliant electrostatic transfer head with cantilever beam and mesa joint supported by a spring support layer in accordance with an embodiment.

FIG. 4 is a plan view illustration and cross-sectional side view illustration taken along line A-A of a bipolar compliant electrostatic transfer head with double sided clamped beam and continuous joint supported by a spring support layer in accordance with an embodiment.

FIG. 5 is a plan view illustration and cross-sectional side view illustration taken along line A-A of a bipolar compliant electrostatic transfer head with a double sided clamped beam including a pair of silicon electrodes with double bends and a mesa joint supported by a spring support layer in accordance with an embodiment.

FIG. 6 is a plan view illustration and cross-sectional side view illustration taken along line A-A of a bipolar compliant electrostatic transfer head with a double sided clamped beam including a pair of silicon electrodes with single bends and a mesa joint supported by a spring support layer in accordance with an embodiment.

FIG. 7 is a plan view illustration and cross-sectional side view illustration taken along line A-A of a bipolar compliant electrostatic transfer head with a double sided clamped beam including a pair of silicon electrodes with double bends and a mesa joint in accordance with an embodiment.

FIG. 8 is a plan view illustration and cross-sectional side view illustration taken along line A-A of a bipolar compliant electrostatic transfer head with a double sided clamped supported beam and pair of silicon electrodes supported by a spring support layer in accordance with an embodiment.

FIG. 9 is a combination cross-sectional side view illustration taken along lines V-V, W-W, X-X, Y-Y, and Z-Z from FIG. 1A in accordance with an embodiment.

FIGS. 10-12 are cross-sectional side view illustrations of a method of forming a base substrate with defined cavities in accordance with an embodiment.

FIGS. 13-14 are cross-sectional side view illustrations of a method of bonding a double SOI stacked wafer to a base substrate with defined cavities in accordance with an embodiment.

FIGS. 15-35 are cross-sectional side view illustrations of a method patterning the bonded structure of FIG. 14 to form a bipolar compliant electrostatic transfer head array with defined cavities in accordance with an embodiment.

FIG. 36 is a combination cross-sectional side view illustration taken along lines W-W, X-X, and Y-Y from FIG. 1A in accordance with an embodiment.

FIGS. 37-38 are cross-sectional side view illustrations of a method of bonding an SOI wafer to a base substrate with defined cavities in accordance with an embodiment.

FIGS. 39-53 are cross-sectional side view illustrations of a method patterning the bonded structure of FIG. 38 to form a bipolar compliant electrostatic transfer head array with defined cavities in accordance with an embodiment.

FIG. 54 is a flow chart illustrating a method of picking up and transferring an array of micro devices from a carrier substrate to a receiving substrate in accordance with an embodiment.

FIG. 55 is a cross-sectional side view illustration of an array of bipolar compliant electrostatic transfer heads positioned over an array of micro devices on a carrier substrate in accordance with an embodiment.

FIG. 56 is a cross-sectional side view illustration of an array of bipolar compliant electrostatic transfer heads in contact with an array of micro devices in accordance with an embodiment.

FIG. 57 is a cross-sectional side view illustration of an array of bipolar compliant electrostatic transfer heads picking up an array of micro devices in accordance with an embodiment.

FIG. 58 is a cross-sectional side view illustration of contacting a receiving substrate with an array of micro devices held by an array of bipolar compliant electrostatic transfer heads in accordance with an embodiment.

FIG. 59 is a cross-sectional side view illustration of an array of micro devices released onto a receiving substrate in accordance with an embodiment.

Detailed description

Embodiments describe micro pick up arrays and compliant electrostatic transfer heads with defined cavities, and methods of transferring micro devices to a receiving substrate. Without being limited to a particular theory, embodiments describe micro pick up arrays and compliant electrostatic transfer heads which operate in accordance with principles of electrostatic grippers, using the attraction of opposite charges to pick up micro devices. In accordance with embodiments, a pull-in voltage is applied to an electrostatic transfer head in order to generate a grip pressure on a micro device and pick up the micro device. For example, the electrostatic transfer head may include a bipolar electrode configuration. The compliant electrostatic transfer head and head arrays in accordance with embodiments may be used to transfer micro devices such as, but not limited to, diodes, LEDs, transistors, MEMS, silicon integrated circuits (ICs) for logic or memory, and gallium arsenide (GaAs) circuits for radio frequency (RF) communications from a carrier substrate to a receiving substrate such as, but is not limited to, a display substrate, a lighting substrate, a substrate with functional devices such as transistors or ICs, or a substrate with metal redistribution lines.

In various embodiments, description is made with reference to figures. However, certain embodiments may be practiced without one or more of these specific details, or in combination with other known methods and configurations. In the following description, numerous specific details are set forth, such as specific configurations, dimensions and processes, etc., in order to provide a thorough understanding of the embodiments. In other instances, well-known semiconductor processes and manufacturing techniques have not been described in particular detail in order to not unnecessarily obscure the embodiments. Reference throughout this specification to “one embodiment,” “an embodiment” or the like means that a particular feature, structure, configuration, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase “in one embodiment,” “an embodiment” or the like in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, configurations, or characteristics may be combined in any suitable manner in one or more embodiments.

The terms “over”, “to”, “spanning”, “between” and “on” as used herein may refer to a relative position of one layer with respect to other layers. One layer “over”, “spanning” or “on” another layer or bonded “to” another layer may be directly in contact with the other layer or may have one or more intervening layers. One layer “between” layers may be directly in contact with the layers or may have one or more intervening layers.

In one aspect, embodiments describe a micro pick up array including an array of compliant electrostatic transfer heads, and method of operation in which the array of compliant electrostatic transfer heads enables improved contact with an array of micro devices as compared to an array of non-compliant transfer heads. In application, as a micro pick up array is lowered onto an array of micro devices, each compliant electrostatic transfer head is independently deflectable toward a cavity. In this manner, each compliant electrostatic transfer head can compensate for variations in height of the micro devices, impurities (e.g. particles) on the micro devices, or surface profile variations of the carrier substrate such as surface waviness. Such compensation can result in reduced compressive forces applied to certain micro devices, leading to protection of the physical integrity of the micro devices and transfer head array. Such compensation can also assist each compliant electrostatic transfer head to make contact with each micro device, and ensure that each intended micro device is picked up. Without the compliant nature of the compliant electrostatic transfer heads an irregular micro device height, wavy carrier substrate, or a particle on a top surface of a single micro device could prevent the remainder of the transfer heads from making contact with the remainder of the micro devices in the array. As a result, an air gap could be formed between those transfer heads and micro devices. With such an air gap, it is possible that the target applied voltage would not create a sufficient grip pressure to overcome the air gap, resulting in an incomplete pick-up process.

In one aspect, embodiments describe compliant electrostatic transfer heads with predefined cavity dimensions (depth, length, width) in which the cavity dimensions are precisely and uniformly determined by the location of confinement layers. In an embodiment, a compliant electrostatic transfer head includes a base substrate, a cavity template layer on the base substrate, a first confinement layer between the base substrate and the cavity template layer, and a patterned device layer on the cavity template layer. The patterned device layer includes an electrode and electrode beam profile that are deflectable toward a cavity in the cavity template layer. A second confinement layer may additionally be located between the cavity template layer and the patterned device layer. In an embodiment, the second confinement layer spans along a top surface of the cavity template layer and directly above the cavity. The second confinement layer may additionally span along sidewalls of the cavity template layer. In an embodiment, the portion of the second confinement layer along sidewalls of the cavity template layer defines, and corresponds to the cavity sidewalls, while the first confinement layer corresponds to a bottom surface of the cavities. In an embodiment, the first and second confinement layers are formed of a dielectric material, such as SiO2. In an embodiment, the cavity template layer is formed of a material, such as silicon, that can be selectively etched relative to the first and second confinement layers.

In another aspect, embodiments describe a manner of fabricating a micro pick up array in which predefined cavity dimensions (depth, length, width) are fabricated at an initial stage, prior to formation of the electrode beam profiles. In an embodiment, a device layer is patterned to include an electrode beam profile above a patterned cavity template layer, and a cavity is then etched in the patterned cavity template layer using one or more confinement layers as etch stop layers. Prior to the etching the cavities, the first and second confinement layers may encapsulate a portion of the cavity template layer, which serves a sacrificial cavity fill material. In an embodiment, selective etch removal of the sacrificial cavity fill material to the first and second confinement layers enables controlled, uniform etching of the cavities. In this manner, the dimensions of the cavities toward which the electrodes and electrode beam profiles deflect may be precisely controlled by the confinement layers, and etch release of the electrode beam profiles can be performed at a terminal stage in the fabrication process, thereby preserving the structural and electrical integrity of the electrodes. Additionally, this may ensure a uniform profile of the array of cavities.

In another aspect, embodiments describe a manner of forming an array of compliant electrostatic transfer heads from commercially available silicon and silicon-on-insulator (SOI) substrates. In an embodiment, defined cavity dimensions are formed in a cavity template layer at an initial fabrication stage prior to bonding an SOI substrate stack to the cavity template layer.

The terms “micro” device or “micro” LED structure as used herein may refer to the descriptive size of certain devices or structures in accordance with embodiments. As used herein, the terms “micro” devices or structures are meant to refer to the scale of 1 to 300 μm, for example, each micro device or electrostatic transfer head including a maximum length or width of a contact surface or mesa structure of 1 to 300 μm. For example, each electrostatic transfer head may include a pair of silicon electrodes, with each silicon electrode including a mesa structure with a maximum width or length of 1 to 300 μm, 1 to 100 μm, or more specifically 1 to 10 μm. In an exemplary embodiment, an electrostatic transfer head has a contact surface of approximately 10 μm by 10 μm. In an embodiment, a bipolar electrostatic transfer head includes a pair of mesa structure of approximately 4.5 μm (width) by 10 μm (length) separated by a 1 μm gap. In another exemplary embodiment, a bipolar electrostatic transfer head having a contact surface of approximately 5 μm by 5 μm includes a pair of mesa structure of approximately 2.25 μm (width) by 5 μm (length) separated by a 0.5 μm gap. However, it is to be appreciated that embodiments are not necessarily so limited, and that certain aspects of the embodiments may be applicable to larger, and possibly smaller size scales.

In some exemplary embodiments, arrays of micro devices which are poised for pick up are described as having a size of 10 μm (in x and/or y dimensions), or size of 5 μm (in x and/or y dimensions). However, it is to be appreciated that embodiments are not necessarily so limited, and that certain aspects of the embodiments may be applicable to larger, and possibly smaller size scales as described above with regard to the electrostatic transfer heads. A transfer tool including an array of compliant electrostatic transfer heads matching an integer multiple of a pitch of the corresponding array of micro devices on a carrier substrate can be used to pick up and transfer the array of micro devices to a receiving substrate. In this manner, it is possible to integrate and assemble micro devices into heterogeneously integrated systems, including substrates of any size ranging from micro displays to large area displays, and at high transfer rates. For example, a 1 cm by 1 cm array of compliant electrostatic transfer heads can pick up and transfer more than 100,000 micro devices, with larger arrays of compliant electrostatic transfer heads being capable of transferring more micro devices.

Referring now to FIG. 1A , a plan view illustration is provided, with views at different depths, for a micro pick up array including an array of bipolar compliant electrostatic transfer heads. In the particular embodiment illustrated, the shaded area illustrates an arrangement of silicon electrodes and silicon interconnects as viewed from the top surface of the bipolar compliant electrostatic transfer head array. The darker shading illustrates a top side via connection as viewed from the top side surface of the bipolar compliant electrostatic transfer head array. Exemplary locations of cavities 136 are illustrated as dotted lines underneath the silicon electrodes. In this manner, the plan view illustration provides detail regarding structures at various depths from a top side of the SOI wafer stack. It is to be appreciated that while FIG. 1A illustrates a bipolar electrode configuration, that embodiments are not limited to bipolar electrode configurations, and embodiments are also applicable to other electrode configurations including monopolar electrode configurations or electrode configurations including more than two electrodes.

As illustrated, the micro pick up array 100 includes an array of compliant electrostatic transfer heads 102 connected to an arrangement of silicon trace interconnects 104 , and bus interconnects 106 . As illustrated, bus interconnects 106 may be formed around a periphery or outside a working area of the micro pick up array including the array of compliant electrostatic transfer heads 102 . In an embodiment, each compliant electrostatic transfer head 102 includes a pair of silicon electrodes 110 , with each silicon electrode 110 including a mesa structure 112 and an electrode lead 114 connected to a silicon interconnect 104 . As illustrated, each compliant electrostatic transfer head 102 is in the form of a double sided clamped beam profile clamped at opposite sides to silicon trace interconnects 104 . As illustrated, a silicon electrode double sided clamped beam may include a pair of silicon electrode leads 114 each with a double bend 115 , and pair mesa structures 112 separated by a mesa dielectric joint 119 that extends in a transverse width of the double sided clamped beam parallel to the pair of silicon interconnects 104 . In such an embodiment, the dielectric joint 119 electrically insulates the pair of silicon electrodes in the bipolar electrode configuration along a transverse width of the double sided clamped beam between the pair of mesa structures 112 . In the particular embodiment illustrated, the beam is in an S-shape configuration, though a variety of other configurations are contemplated. In the embodiment illustrated, the array of mesa structure 112 pairs in the micro pick up array 100 are arranged with approximately the same pitch as the micro devices to be picked up, and placed, for example, corresponding to a pixel pitch on a display substrate for exemplary micro LED devices.

In an embodiment, a plurality of vias 120 are formed through the micro pick up array SOI stack to provide a backside electrical contact to interconnects 106 in order to electrically connect the silicon electrodes 110 with working circuitry of a transfer head assembly. In the embodiment illustrated in FIG. 1A , the interconnect 106 on the left side of the illustration may be connected to a first voltage source V.sub.A, and the interconnect 106 on the right side of the illustration may be connected to a second voltage source V.sub.B. Where each compliant electrostatic transfer head 102 is operable as a bipolar electrostatic transfer head, voltage sources V.sub.A and V.sub.B may simultaneously apply opposite voltages so that each of the silicon electrodes 110 in a respective compliant electrostatic transfer head 102 has an opposite voltage.

FIG. 1B is a close-up plan view illustration of a single bipolar compliant electrostatic transfer head 102 of FIG. 1A . As illustrated, the double sided clamped beam includes a pair of silicon electrode leads 114 with double bends 115 and a mesa joint 119 between mesa structures 112 , all of which may be optionally supported by a spring support layer 150 . For example, the description made with regard to FIGS. 13-35 is made with regard to a double SOI stacked wafer including spring support layer 150 , while the description made with regard to FIGS. 37-53 is made with regard to an SOI stacked wafer that does not include spring support layer. Accordingly, illustration of spring support layer 150 in FIGS. 1B-8 is optional.

Referring again to FIG. 1B , the silicon electrodes form an electrode beam profile, and the optional spring support layer 150 forms a spring support layer beam profile underneath and supporting the electrode beam profile, where the spring support layer beam profile is wider than the supported electrode beam profile. A cavity 136 is formed within the cavity template layer 154 and the electrode beam profile and spring support layer beam profile are deflectable toward the cavity 136 . In an embodiment, a separate cavity 136 is formed underneath each compliant electrostatic transfer head 102 . In an embodiment, a single cavity 136 spans underneath multiple compliant electrostatic transfer heads 102 .

FIG. 1C is a cross-sectional side view illustration taken along transverse line C-C of the bipolar compliant electrostatic transfer head illustrated in FIG. 1B in accordance with an embodiment. In the embodiment illustrated in FIG. 1C , each silicon electrode 110 in a bipolar electrode configuration extends from a separate silicon interconnect 104 . FIG. 1D is a cross-sectional side view illustration taken along longitudinal line D-D of the bipolar compliant electrostatic transfer head illustrated in FIG. 1B in accordance with an embodiment. As illustrated in FIGS. 1C-1D , both the silicon electrode mesa structures 112 and leads 114 extend over and are deflectable toward a cavity 136 between the base substrate 130 and the silicon electrode 110 .

As illustrated in FIGS. 1C-1D , a first confinement layer 156 is located between the base substrate 130 and cavity template layer 154 . A second confinement layer 152 may be formed between the cavity template layer 154 and patterned device layer 140 . In the embodiment illustrated, second confinement layer 152 is located between the cavity template layer 154 and optional spring support layer 150 . As shown, the second confinement layer 152 spans along a top surface of the cavity template layer 154 and directly above the cavity 136 . The second confinement layer 152 may additionally span along sidewalls of the cavity template layer 152 , defining sidewalls of the cavity 136 . Alternatively, separate confinement layers can be used along the top surface and sidewalls of the cavity template layer 154 .

In an embodiment, a separate cavity 136 is formed underneath each bipolar silicon electrode 110 in the micro pick up array and between two separate silicon interconnects 104 . In an embodiment, a single cavity 136 is formed underneath an array of bipolar silicon electrodes 110 and between two separate silicon interconnects 104 . Referring again to FIG. 1A , a single or multiple separate cavities 136 can be formed between arrays of silicon interconnects 104 . In an embodiment, cavities 136 are the same cavity. Trenches 116 may also be formed in the patterned silicon layer defining the silicon electrodes 110 and silicon interconnects 104 , 106 as described in more detail in the following description.

FIGS. 2-8 illustrate various modifications of bipolar compliant electrostatic transfer heads spanning between silicon interconnects 104 in accordance with embodiments. While FIGS. 2-8 are illustrated separately from the detailed processing sequences illustrated in FIGS. 10-35 and FIGS. 37-53 , it is to be appreciated that many of the various modifications described with respect to FIGS. 2-8 can be implemented into the processing sequences. Similar to FIG. 1A , for clarity purposes, only a single bipolar compliant electrostatic transfer head 102 is illustrated in FIGS. 2-8 as spanning between two silicon trance interconnects 104 , though an array of bipolar electrostatic transfer heads may span between the silicon interconnects 104 in accordance with embodiments. Also, similar to the single bipolar compliant electrostatic transfer head described with regard to FIGS. 1B-1D , FIGS. 2-8 each illustrate an electrode beam profile, optional spring support layer beam profile, and defined cavity 136 .

FIG. 2 is a plan view illustration and cross-sectional side view illustration taken along line A-A of a bipolar compliant electrostatic transfer head with cantilever beam and continuous joint in accordance with an embodiment. As illustrated, a silicon electrode cantilever beam may include a pair of silicon electrode leads 114 extending from two silicon interconnects 104 , and pair mesa structures 112 separated by a continuous dielectric joint 119 which extends in a longitudinal length of the cantilever beam parallel to the pair of silicon interconnects 104 , all optionally supported by a spring support layer 150 . In such an embodiment, the dielectric joint 119 electrically insulates the pair of silicon electrodes in the bipolar electrode configuration along a longitudinal length of the cantilever beam along both the pair silicon electrode leads 114 and pair of mesa structures 112 . As illustrated, the silicon electrode leads 114 may include a bend 115 (illustrated as a 90 degree bend).

FIG. 3 is a plan view illustration and cross-sectional side view illustration taken along line A-A of a bipolar compliant electrostatic transfer head with cantilever beam and mesa joint in accordance with an embodiment. As illustrated, a silicon electrode cantilever beam may include a pair of silicon electrode leads 114 extending from two silicon interconnects 104 , and pair mesa structures 112 separated by a mesa dielectric joint 119 which extends in a longitudinal length of the cantilever beam parallel to the pair of silicon interconnects 104 , all optionally supported by a spring support layer 150 . In such an embodiment, the dielectric joint 119 electrically insulates the pair of silicon electrodes in the bipolar electrode configuration along a longitudinal length of the cantilever beam along the pair of mesa structures 112 . As illustrated, the pair of silicon electrode leads 114 are physically separated by patterning and may include a bend 115 (illustrated as a 90 degree bend).

FIG. 4 is a plan view illustration and cross-sectional side view illustration taken along line A-A of a bipolar compliant electrostatic transfer head with double sided clamped beam and continuous joint in accordance with an embodiment. As illustrated, a silicon electrode double sided clamped beam may include a pair of bent silicon electrode leads 114 extending from two silicon interconnects 104 , and pair mesa structures 112 separated by a continuous dielectric joint 119 which extends in a longitudinal length of the cantilever beam parallel to the pair of silicon interconnects 104 , all optionally supported by a spring support layer 150 . In such an embodiment, the dielectric joint 119 electrically insulates the pair of silicon electrodes in the bipolar electrode configuration along a longitudinal length of the double sided clamped beam along both the pair silicon electrode leads 114 and pair of mesa structures 112 . As illustrated, the silicon electrode leads 114 may each include bends 115 (illustrated as 90 degree bends) at proximal and distal locations where the electrode leads extend from the silicon interconnects 104 .

FIG. 5 is a plan view illustration and cross-sectional side view illustration taken along line A-A of a bipolar compliant electrostatic transfer head with a double sided clamped beam including a pair of silicon electrodes with double bends and a mesa joint in accordance with an embodiment. As illustrated, a silicon electrode double sided clamped beam may include a pair of silicon electrode leads 114 extending from two silicon interconnects 104 , each lead 114 with a double bend 115 , and pair mesa structures 112 separated by a mesa dielectric joint 119 which extends in a transverse width of the double sided clamped beam parallel to the pair of silicon interconnects 104 , all optionally supported by a spring support layer 150 . In such an embodiment, the dielectric joint 119 electrically insulates the pair of silicon electrodes in the bipolar electrode configuration along a transverse width of the cantilever beam between the pair of mesa structures 112 , and the pair of silicon electrode leads 114 are physically separated by patterning. In the embodiment illustrated, each electrode lead 114 is split, so that the beam configuration assumes an 8-shape configuration with the silicon electrode leads 114 .

FIG. 6 is a plan view illustration and cross-sectional side view illustration taken along line A-A of a bipolar compliant electrostatic transfer head with a double sided clamped beam including a pair of silicon electrodes with single bends and a mesa joint in accordance with an embodiment. As illustrated, a silicon electrode double sided clamped beam may include a pair of silicon electrode leads 114 extending from two silicon interconnects 104 , each lead 114 with a single bend 115 , and pair mesa structures 112 separated by a mesa dielectric joint 119 extends in a transverse width of the double sided clamped beam perpendicular to the pair of silicon interconnects 104 , all optionally supported by a spring support layer 150 . In such an embodiment, the dielectric joint 119 electrically insulates the pair of silicon electrodes in the bipolar electrode configuration along a transverse width of the double sided clamped beam between the pair of mesa structures 112 , and the pair of silicon electrode leads 114 are physically separated by patterning.

FIG. 7 is a plan view illustration and cross-sectional side view illustration taken along line A-A of a bipolar compliant electrostatic transfer head with a double sided clamped beam including a pair of silicon electrodes with double bends and a mesa joint in accordance with an embodiment. As illustrated, a silicon electrode double sided clamped beam may include a pair of silicon electrode leads 114 each with a double bend 115 , and pair mesa structures 112 separated by a mesa dielectric joint 119 which extends in a transverse width of the double sided clamped beam parallel to the pair of silicon interconnects 104 , all optionally supported by a spring support layer 150 . In such an embodiment, the dielectric joint 119 electrically insulates the pair of silicon electrodes in the bipolar electrode configuration along a transverse width of the double sided clamped beam between the pair of mesa structures 112 . In the particular embodiment illustrated in FIG. 7 , the beam is in a W-shape configuration.

FIG. 8 is a plan view illustration and cross-sectional side view illustration taken along line A-A of a bipolar compliant electrostatic transfer head with a double sided clamped beam including a pair of silicon electrodes and a mesa joint in accordance with an embodiment. As illustrated, a silicon electrode double sided clamped beam may include a pair of silicon electrode leads 114 and a pair mesa structures 112 separated by a mesa dielectric joint 119 which extends in a transverse width of the double sided clamped beam parallel to the pair of silicon interconnects 104 , all optionally supported by a spring support layer 150 . In such an embodiment, the dielectric joint 119 electrically insulates the pair of silicon electrodes in the bipolar electrode configuration along a transverse width of the double sided clamped beam between the pair of mesa structures 112 .

Referring now to FIG. 9 a combination cross-sectional side view illustration is provided taken along lines V-V, W-W, X-X, Y-Y, and Z-Z from FIG. 1A in accordance with an embodiment. The combination view is not a representation of the precise relative locations for all of the different features illustrated, rather the combination view combines specific features at different locations previously identified in FIG. 1A in order to more easily represent the particular variations in processing sequences. For example, while the combination cross-sectional side view illustration shows one via 120 corresponding to one silicon electrode 110 , it is clear from FIG. 1A that one via 120 may be electrically connected with a plurality of silicon electrodes 110 along one or more interconnects 104 . As illustrated, lines W-W and Y-Y are along vias 120 . As illustrated, lines V-V and Z-Z are along one or more trenches 116 defining the silicon electrodes 110 and silicon interconnects 104 , 106 . As illustrated, line X-X is across a bipolar compliant electrostatic transfer head including a pair of silicon electrodes 110 . Referring again to FIG. 1A , one or more cavities 136 may be formed around and beneath all silicon electrodes 110 , and between interconnects 104 , 106 .

The description continues in the full USPTO document.